1. Field of the Invention
The present invention relates to a vertical gallium nitride-based light emitting diode (hereinafter, referred to as a vertical GaN-based LED) and a method of manufacturing the same, which can increases light extraction efficiency, thereby enhancing external quantum efficiency.
2. Description of the Related Art
Generally, GaN-based LEDs are grown on a sapphire substrate. The sapphire substrate is a rigid nonconductor and has a low thermal conductivity. Therefore, it is difficult to reduce the size of the GaN-based LED for cost-down or improve the optical power and chip characteristics. Particularly, heat dissipation is very important for the LEDs because a high current should be applied to the GaN-based LEDs so as to increase the optical power of the GaN-based LEDs. To solve these problems, a vertical GaN-based LED has been proposed. In the vertical GaN-based LED, the sapphire substrate is removed using a laser lift-off (hereinafter, referred to as LLO) technology.
In general vertical GaN-based LEDs, however, efficiency where photons to be generated from an active layer are emitted to the outside is degraded. That is, luminance is degraded.
To solve such a problem, surface irregularities formed at even or uneven intervals are provided in a conventional vertical GaN-based LED, thereby enhancing luminance.
Now, a conventional vertical GaN-based LED will be described with reference to FIGS. 1 and 2. FIGS. 1 and 2 are perspective views illustrating the conventional vertical GaN-based LED.
Referring to FIGS. 1 and 2, the conventional vertical GaN-based LED has a positive electrode (p-electrode) 130 formed on a structure support layer 150. On the p-electrode 130, a p-type GaN layer 126, an active layer 124, and an n-type GaN layer 121 are sequentially formed, thereby forming a light-emission structure 120.
On the light-emission structure 120, that is, on the surface of the n-type GaN layer 126, an irregular-surface structure 160 for enhancing light extraction efficiency is formed. On the irregular-surface structure 160, a negative electrode (n-electrode) 170 is formed.
More specifically, FIG. 1 shows a state where the irregular-surface structure 160 of the n-type GaN layer 126 has irregularities formed at even intervals. FIG. 2 shows a state where the irregular-surface structure 160 of the n-type GaN layer 126 has irregularities formed at uneven intervals.
However, when the irregular-surface structure 160 of the n-type GaN layer 126 is formed at even or uneven intervals as described above, the surface where surface irregularities can be formed, that is, the surface of the n-type GaN layer is limited. Therefore, an improvement effect of luminance is not enough.
Therefore, a new method for maximizing an improvement effect of luminance is being required in this technical field.